Microsoft are taking down thier chatrooms for several reasons.
Currently there are multiple lawsuits against Microsoft pertaining to incidents not dissimilar to the US Marine one earlier this year.
Although chatroom attacks are few and far between, the number is growing worryingly - kids aren't taking enough precautions because they think thier safe, and sick individuals are taking more and more advantage of this.
The real major push to finally close them however are the recent MSBlast attacks ... this affected almost the entire Microsoft Network and crippled thier operations for over a week.
Attacks like this are also becomming more and more dangerous and commonplace as well. Alot of Anti-Microsoft groups and individuals are really starting campaigns for lack of a better word of terrorism.
The Chatrooms were the stepping-stone for the MSBlast virus, which very very quickly infected an estimated 4million systems within a matter of a week.
Quite frankly everything that Microsoft has had to endure the past year with alot escellation and media coverage, it is surprising that they have kept these rooms online as long as they have.
To be honest i'm getting truely sick of the current Anti-Microsoft stance from people...
quite frankly alot of the online behaviour now is just sickening.